Coastal ecosystems for DRR and CCA:

mangroves and other coastal vegetation

Fabrice Renaud

United Nations University

Institute for Environment and Human Security

Intensive Summer Course

Advancing DRR to enhance sustainable development

in a changing world

20 June / 1 July 2016, Bonn, Germany

Outline

Some benefits from coastal vegetation

Case study Sri Lanka (tsunami context)

Brief Example from 2011 Great East Japan

Earthquake and Tsunami

Brief Example of Coastal Erosion in North

Central Java, Indonesia

Brief Example from salinity intrusion in the

Mekong Delta, Vietnam

Some benefits from coastal

vegetation

Protection of coastal zones

with ecological approaches

Ph

oto

s b

y F

ab

rice

Re

na

ud

/UN

U-E

HS

Extension, production and losses of

vegetated coastal ecosystems

Source: Duarte et al (2013): The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate Change

DOI: 10.1038/NCLIMATE1970

Loss of Mangroves Globally

Source: http://gfw.blog.s3.amazonaws.com/2015/02/Tree-Cover-Loss-chart-a_global.jpg

Some services provided by

vegetated coastal ecosystems

Source: Duarte et al (2013): The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate Change

DOI: 10.1038/NCLIMATE1970

Elevation/Accretion Rates

“our e: TABLE → Duarte et al : The role of coastal plant communities for climate change mitigation and adaptation. Nature Climate

Change DOI: . /NCLIMATE . FIGURE“ → M Ivor et al : The response of mangrove soil surface elevation to sea level rise.

Natural Coastal Protection Series: Report 3. The Nature Conservancy

Accomodation Space

Source: McIvor et al (2013): The response of mangrove soil surface elevation to sea level rise. Natural Coastal Protection Series: Report 3. The

Nature Conservancy

Case study Sri Lanka

Tsunami Impacts

• Close to 250.000 deaths

for the entire Indian

Ocean basin

• Several millions displaced,

loss of livelihoods, etc. © AFP/Getty Images; SOURCE: UNEP, 2005

SOURCE: Titov et al. 2005. DOI: 10.1126/science.1114576

11

Exposure: Buffering the

Populations

Following the tsunami, the fact that some ecosystem components had previously been degraded by human interventions was blamed for the damages & losses:

• Costal vegetation in general and mangroves in particular

• Sand dunes

• Sea grasses

• Coral reefs

It was assumed that these features would have protected the population by:

• Reducing the energy of the waves

• Reducing the exposure of the populations (increased distance from coastline)

12

Destruction of Natural

Buffers

• Specific effects of some

ecosystem components are

scientifically debated when

it comes to the tsunami

Photo by Marcus Kaplan

13

Did Natural Features Limit

the Impact? Kathiresan & Rajendra. Estuarine, Coastal & Shelf Sci 65:601-606

Kerr et al. Estuarine, Coastal & Shelf Sci 67:539-541

• Performed stepwise regression analysis on data

from Kathiresan

• Conclusion: vegetation area contributes little to

explanation of variation in mortality

Kathiresan & Rajendra. Estuarine, Coastal & Shelf Sci 67:542

• Did not really address the statistical questions put

forward by Kerr et al. but stood by their conclusions

Vermaat & Thampanya. Estuarine, Coastal & Shelf Sci 69:1-3

• Performed an ANOVA with distance and elevation

as covariates

• Conclusion: interpretation by Kathiresan and

Rajendra holds

Vermaat & Thampanya. Estuarine, Coastal & Shelf Sci (in press)

• Erratum Mistake in stats: mortality and

property loss were not less behind mangroves

14

Some Factors at Play – but

much more Research needed

• There are many potential factors to consider incl.:

– Bathymetry

– Topography

– Distance of settlement

– Coastal vegetation

– Impact angle

– Distance from epicentre

• Chatenouy & Pedduzzi:

– Depth of sea floor at 10km

– Length of proximal slope

– % protection from seagrass

– Distance from fault line

– % protection from coral

Source: Chatenoux & Peduzzi. Natural Hazards. DOI 10.1007/s11069-

006-0015-9

15

Source: PhD research of Marcus Kaplan (UNU-EHS)

Tsunami, Coastal Vegetation and Vulnerability

16

Tsunami, Coastal Vegetation and Vulnerability

Source: PhD research of Marcus Kaplan (UNU-EHS)

17

Brief Example from 2011 Great East

Japan Earthquake and Tsunami

Earthquake and Tsunami impact in

Sendai, Wakabayashi Ward, Arahama

District

19

23/09/2003 17/04/2011

04/10/2011 29/03/2012

Photo Credit: Tohoku Construction Association . Do not reproduce

Coastal Forests in Sendai

20

Photo Credit: Fabrice Renaud/UNU-EHS Do not reproduce

Resistance of trees

Trunk bending and breaking were closely related to tsunami water depth and hydrodynamic parameters

Tree overturning was found to be more site specific, and the root-soil strength greatly affected the critical value

Debris trapping but also secondary damage to people and buildings

Source: Tanaka et al (2012): Breaking pattern and critical breaking condition of Japanese pine trees on coastal sand dunes in huge tsunami caused by Great East Japan

Earthquake. Nat Hazards 65:423–442

Issues with engineering

solutions

Source: Tanalka et al (2012): Coastal and estuarine morphology changes induced by the 2011 Great East Japan Earthquake Tsunami. Coastal Engineering Journal 54(1): DOI:

10.1142/S0578563412500106

Ecosystem and DRR in the context

of the Great East Japan Earthquake

The Earthquake Disaster Reconstruction Plan (City of Sendai, 2011)

• Puts some emphasis on the environment

• Addresses agricultural issues

• Restore the eautiful oast

• Utilising ostal prevention forests e pli itl mentioned

23

Ecosystem and DRR in the context of the

Great East Japan Earthquake

24

Source: Sendai City Earthquake Disaster Reconstruction Plan (2011)

Devastation in Minamisanriku & plans

for relocation

25

Ph

oto

Cre

dit

: F

ab

rice

Re

na

ud

/UN

U-E

HS

Do

no

t re

pro

du

ce

Brief Example of Coastal Erosion in

North Central Java, Indonesia

Coastal inundation –

Central Java

Source: Marfai (2011): Impact of costal inundation on ecology and agricultural land use. Case study in Central Java, Indonesia. Quaestiones

Geographicae 20:19-32

Study Case in Demak

Some measures taken in the region1/2

Double layer wall Failed single layer wall

Some measures taken in the region1/2

Building with nature –

Indonesia - video

Source: https://www.youtube.com/watch?v=3iv4pv3c0Io

Brief Example from Salinity Intrusion

in the Mekong Delta, Vietnam

Example: Changes in agro-ecosystems in the Mekong Delta in Vietnam

• 39,000 km2

• 18 million inhabitants

• 2/3 used for agriculture

• Supplies: – 50% of staple food

– 50% fisheries

– 60% fruit production

Image/Sensor: MODIS

Some social & economic characteristics

Some restrictions in terms of agricultural production:

• Governmental control over rice production

• Lack of land tenure

• Limited access to capital

• Limited direct access to markets

• Price fluctuations (inputs and outputs)

Reduction in poverty rate (23% in 2002 to 12% in 2008), but high disparities remain

Lags behind on many socio-economic indicators related to housing, access to water and sanitation, health care, education, etc.

Garschagen et al (2012): Socio-economic development in the Mekong Delta: Between the prospects for progress and the realm of

reality. In Renaud and Kuenzer (eds), The Mekong Delta System. Interdisciplinary Analyses of a River Delta, Springer, pp83-132.

Pressure from upstream

Source: Kuenzer et al (2012): Understanding the impact of hydropower developments in the

context of upstream–downstream relations in the Mekong river basin. Sustainability Science

DOI 10.1007/s11625-012-0195-z

Climate Change:

• More extreme events

• Dams playing a more significant role

Pressure from downstream

Source: Carew-Reid (2008): Rapid assessment of the extent and impact of sea level rise in Viet Nam. ICEM – International Centre

for Environmental Management

Project Location

Agroecosystems in Ben Tre

Rice System

Rice – Prawn System

Photo: UNU-EHS/Huong

Intensive Shrimp System

Photo: UNU-EHS/Huong

Photo: UNU-EHS/Huong

Intensive Shrimp Syst

Differences between

Agroecosystems

Rice System Rice – extensive shrimp

System

Intensive Shrimp System

Freshwater

Protected by system of

dyke and sluice gate

Low investment

Low return

Low ability to invest

Low risk

Freshwater and saline water

No protection against salinity

Medium inverstment

Low/Medium return

Some ability to invest

Low risk

Saline water

No protection against salinity

High investment

High return

High ability to invest

High risk

Historical Changes in Agroecosystems

Sub-regions I & II

Results from Focus Group Discussions , Household and expert interviews

SR Major changes Year Reasons for Change

I Single rice crop (local varieties) and

natural shrimp stock cultivation

< 1997 • Seasonal salinity intrusion

• No embankments

Double rice cropping (modern &

local varieties)

1997 -2000

• Policies for agriculture and aquaculture development,

• Fresh water dyke construction

• Improved irrigation and transport systems

Double rice, triple rice, coconut

trees and vegetables

> 2000 • Completed embankment and sluice gates

• Economic interests (triple rice, coconut)

II Single rice crop (local varieties) and

natural stock shrimp cultivation

<1995 • Seasonal salinity intrusion

• Low agriculture and aquaculture productivity

Single rice crop (local varieties) –

extensive shrimp cultivation

1995-2000 • Decrease in natural shrimp resource

• Government development policies

Single rice crop (local & new

varieties) – extensive & intensive

shrimp cultivation

2000 -2006 • High market prices

• Decision 02 on Aquaculture Development

• Infrastructure (irrigation, electricity and transportation)

• New technologies (new varieties, training)

Return to the rice-extensive shrimp

production

> 2009 • Shrimp diseases

• Water pollution

• Lack of financial assets

Potential adaptation to salinity intrusion

http://wwf.panda.org

Huong/UNU-EHS (2011)

Huong/UNU-EHS (2011)

Huong/UNU-EHS (2011) Renaud/UNU-EHS (2013)

Low flows and

Salinity intrusion

Advantages and shortcomings of selected approaches to

address salinity intrusion – Case of Ben Tre Province

Options Effects on

agroecosystems

Environmental

externalities

Potential social

consequences

Contribution to resilience

Infrastructure

development

Rice-based systems

can be maintained or

intensified

Generation of pollution

within and outside the

protected system

In the absence of crop

rotation, increasing use

of agrichemicals

Effect on sediments and

discharge

Could result in a

poverty trap for some

rice farmers if no

diversification is

possible

Social tensions

Little diversification so fragile system

in case of severe pest

outbreaks or failure to control salinity

Loss of capacity to adapt to

other environmental changes if

remain with one production

system

Ecosystem-based

approaches

Some land would

need to be converted

back to natural

vegetation

Increase in

biodiversity

No direct externalities Some farms would

need to be relocated

Resilience would be

increased as the

buffering effect would

limit the chances of

damages along the

coast and further

inland

River flow

regulation

Current agro-

ecosystems can

be maintained

Reduction in extent of

brackish water

systems

Important externalities

in areas directly

affected by dam

construction

Alteration of sediment

and nutrient flows

Reduced stress on

agricultural system

would be beneficial

as long as this is

accompanied by

livelihood

diversification

Resilience could

increase but for the

most part the region

would be dependent

on decisions taken

upstream

Source: Renaud et al (2014): Resilience and shifts in agro-ecosystems facing increasing sea-level rise and salinity intrusion in Ben Tre Province,

Mekong Delta. Climatic Change

Advantages and shortcomings of selected approaches to

address salinity intrusion – Case of Ben Tre Province

Options Effects on

agroecosystems

Environmental

externalities

Potential social

consequences

Contribution to resilience

Agronomic

approaches

Short cycle varieties

would prove very

useful. Development of

further rice salinity

tolerant varieties could

be outpaced by

increased salinity

intrusion

No direct

externalities

Preserve current

system in short

term

but failure of

system

in the longer term

is

possible

Adapting rice to salinity without

further crop diversification,

salinity will compromise rice

production eventually

Shifts in

Agro-

ecosystems

Diversification of

production systems is a

good short-term

solution. Improved

water management

practice needed

Possibly abandon rice

production in all regions

in the longer term

Increase in

salinity intrusion

further

Inland

Can allow to

develop livelihoods

adapted to both

water systems,

leading to

diversification of

agricultural

production.

Adapted system

Increased resilience as

agricultural systems adapted to

the environmental

circumstances

More opportunities to innovate

would exist

Source: Renaud et al (2014): Resilience and shifts in agro-ecosystems facing increasing sea-level rise and salinity intrusion in Ben Tre Province,

Mekong Delta. Climatic Change

Diversified systems vs.

Intensified systems

Photos: F. Renaud/UNU-EHS (2011-2013)

THANK YOU!

UNITED NATIONS UNIVERSITY

Institute for Environment

and Human Security (UNU-EHS)

Platz der Vereinten Nationen 1

53113 Bonn, Germany

e-mail: renaud@ehs.unu.edu

www.ehs.unu.edu